5 Replies Latest reply on Mar 2, 2014 3:18 PM by erolst

    How to prevent duplicates in join table?


      I need to know how to prevent duplicates in a join table.


      I am building a restaurant inventory database. I have three tables: Restaurants, Products and a join table between them. The restaurant and the products tables both have numeric primary keys. The join table has foreign keys that are related to the respective parents. How do I prevent duplicates like the ones shown below?


      Restaurant IDProduct IDQtyMy Comments
      11100This is ok.
      1250This is ok.
      11200Not ok; this is a duplicate because the restaurant ID and product ID match the values in the first record.
      2150This is ok.
      2275This is ok.